A fingerprint verification device is used to compares a fingerprint image, which has been collected from a person to be identified, with registered fingerprint images in order to determine whether or not the fingerprint of the person to be identified matches one of the fingerprints of the registered persons. Whether the two corresponding fingerprint images match or not is determined in such a manner that characteristic information(e.g., such as minutia (i.e., characteristic point) or a spectrum characteristic, which is used in order to identify the fingerprint image), which have been extracted from the respective fingerprint images, are compared with each other. Therefore, the fingerprint image verification device includes a memory that stores characteristic information extracted from the fingerprint images of the registered persons. When the fingerprint is verified, characteristic information, which is extracted from the fingerprint image of the person to be identified, is compared with each pre-stored characteristic information, thereby determining whether the two corresponding fingerprint images match or not.
Some type of such a fingerprint verification device eliminates the need to input auxiliary identification information such as an ID code, and compares a fingerprint image of a person to be identified with all the registered fingerprint images. This type of fingerprint verification device has a problem that as the number of registered fingerprints increases, the verifying time becomes longer. In order to solve the problem, several technologies (e.g., Japanese Laid-open Patent Publication No. 10-187970) have been developed, in which the registered fingerprints that will be used for verification (i.e., identity determination) of the fingerprint of the person to be identified are narrowed down in advance and only the narrowed registered fingerprints are compared with the person's fingerprint.
In the fingerprint verification device described in the above-mentioned publication, the registered fingerprints are categorized and stored according to fingerprint patterns. After the fingerprint image of the person to be identified is collected, a fingerprint pattern is obtained from the fingerprint image. Then, fingerprint images belonging to the same category as the obtained fingerprint pattern are selected from the registered fingerprints. Subsequently, the characteristic information of each fingerprint image belonging to the selected category is compared with the characteristic information of the collected fingerprint image.
However, in the technology described in the publication, in addition to the characteristic information that is necessary in order to determine the identity of the fingerprint image, auxiliary information such as the fingerprint pattern must be extracted from the fingerprint image of the person to be identified. In order to extract the auxiliary information, an additional process is required, which makes the system complex.
Accordingly, it is an object of the present invention to provide fingerprint verification technologies whereby registered fingerprint images that are used for verification (i.e., identity determination) can be narrowed down without extracting auxiliary information, such as a fingerprint pattern, from a collected fingerprint image.